Method of electrodepositing cobalt and chromium



Patented Aug. id, 1923.

burrs cram orrica.

I HARRY CREIGHTON' PEIEFER AND HARRIE CLARK PIERCE, 01? LA FAYETTE, INDIANA, A SSIGNORS TO JAMES CLARENCE PATTEN, F KOKOMO, INDIANA.

mn'rnon 6r nnncrnonnrosrrme COBALT AND GHROMIUM.

No Drawing.

,, maybe prepared as follows:

issolve 15 grams of chromic oxid (C30,) in c. 0. hot concentrated hydrochloric acid; dilute with Water to 125 c. c.

and add 35 grams calcium chlorid (CaCI 20 2 grams sodium chlorid (NaCl) and 15 grams cobaltous chlorid (C'OCl The relative proportions of the ingredients of such a bath'would be as follows: 7

Cr O- q 120 g. HCl (Cone) I 200 0.0. Gaol,- 280g. 'N'aGl 16g. CoCl V, 120 g. H 0 8000.0;

We may use an anode of pure cast chromium, and a cathode of cleaned and polished sheet steel or other metal.

' Instead of a chromium anode we may use an alloy of cobalt and chromium (such as an alloy containing 7 5% cobalt and 25%, chro mium), in wlncli case the bath may have the following composition:

Instead of NaCl, an equivalent amount of CoCl may be used.

' In carry-mg out the electrodeposition a Application .filed August 5, 1920. Serial No. 401,486.

current density of 1 to 2 a-mperes per square inclr is used and the bath is preferably maintained at a temperature of from 70 to 80 C. The cobalt content of the bath must not be allowed to get too low, or the cathode deposit instead of being hard and shiny, will be crumbly and dark. The addition of clove oil seems to have a beneficial effect on the de- Y posit. 5 to 6 drops of clove oil are dissolved in 4 5 c. 0. alcohol and several drops of this solution are addedto the bath from time to time. The clove oil further serves to keep the bath from foaming;

In case the bath tends to thicken after being used forsome time, suflicient water is added to keep the volume of the solution constant.

It is generally preferable to electrolyze or age the bath for about an hour and a half during which time the deposit may consist only of cobalt. Thereafterthe deposit consists of a hard firmly adherent coating or plate of chromium and cobalt.

While we prefer to use soluble metallic anodes, as above described, an insoluble anode, such as a carbon anode, may be used.

- It will be further understood that our inven tion is not limited to the use of the precise proportions of ingredients above specified. The term anode containing chromium is used in the claims to'designate both chromium metal and chromium alloys.

We claim 1. The method of obtaining deposits of cobalt chromium alloy resistant to the action of practically all atmospheric conditions and practically immune to the action of all organic and mineral acids, which consists in passing an electric current thru a bath con- 7 taining chromium and cobalt compounds,

the temperature of the bath and the current density being so controlled as to produce a hard adherent deposit of cobalt and chromium.

2. The process as claimed in claim 1 in which an anode containing chromium is used.

3. The process as claimed in claim 1 in which the anode is a cobalt-chromium alloy.

Q it 1,465,173

4. The 'process as claimed in claim 2 in 70 to 80 C. and a current density of from which the bath contains chlorids of cobalt one to two amperes per square inch is em- 10 and chromium. ployed. v

5. The process as claimed in claim 3 in In testimony whereof, we affix our signa- 6 which the bathcontains also calcium and sotures.

dium chlorids.

6. The process as claimed in claim 1 in HARRY CREIGHTON PEFFER, which the temperature is maintained at from HARRIE CLARK PIERCE. 

